Here is the full list of all 33 Killing Zombies achievements.
Buy the MP5-Navy
10,000 Lifetime Damage
Buy the Sledge Hammer
Buy the MP5
Buy the 1911
1,000 Lifetime Damage
Play Killing Zombies on Halloween
100,000 Lifetime Damage
1,000,000 Lifetime Damage
Buy the Golf Club
Buy the Crowbar
Buy the Axe
Buy the Wrench
Buy the Hammer
Buy the Baseball Bat
Buy the Police Baton
Buy the Pitch Fork
Buy the Gloc
Buy the Magnum Revolver
Buy the Minigun
Buy the Sawn Off Shotgun
Buy the Combat Shotgun
Buy the M1 Garand
Buy the Bolt Action Sniper Rifle
Buy the Fifty Caliber Sniper Rife
Buy the MP40
Buy the Thompson
Buy the Uzi
Buy the AK47
Buy the M16
Buy the SCAR
Buy the SAW
Buy the Grenade Launcher